Distribute 'items' in buckets equally (best effort)

algorithm, distribution, java, math

Solution

This type of thinking should work:

package sandbox;

public class Sandbox
{

    public static void main(String[] args)
    {
        int numBuckets = 12;
        int numItems = 34;

        int itemsPerBucket = (numItems / numBuckets);
        int remainingItems = (numItems % numBuckets);

        for (int i = 1; i <= numBuckets; i++)
        {
            int extra = (i <= remainingItems) ? 1:0;
            System.out.println("bucket " + i + " contains " + (itemsPerBucket + extra) + " items.");
        }
    }
}

The output of this:

bucket 1 contains 3 items.
bucket 2 contains 3 items.
bucket 3 contains 3 items.
bucket 4 contains 3 items.
bucket 5 contains 3 items.
bucket 6 contains 3 items.
bucket 7 contains 3 items.
bucket 8 contains 3 items.
bucket 9 contains 3 items.
bucket 10 contains 3 items.
bucket 11 contains 2 items.
bucket 12 contains 2 items.

Notice the only looping you do is to talk about each bucket. You can easily just ask a bucket number and see how many items are in it without loop!

Problem

Say I want to distribute `y` items to `x` buckets evenly. If `x` is a multiple of `y` this distribution will be even, if not I can end up with `0` items in each bucket. For ex: For ex: I have `3` buckets and I want to distribute `2` items each. Since doing the division `(2/3)` will lead to `0` items per bucket. How can I achieve, a distribution of `1`, `1`, `0`?

Original source